Heatsinking LED Emitters (No Star)

[chris89]

Hi,

I bought some LEDs for a project (not a flashlight) and (foolishly) didn't get them with a heatsink of any kind. I just got some Optek OVTL01LGA 1W emitters. I really want to avoid spending much more money and am unable to get metal-core PCB where I am, so I'd like to use what I've got, if that's possible.

24 LEDs are going in a 5"x7" square. What had occurred to me as a practical way to cool the LEDs was to add a copper fill around each LED's cathode of a couple square inches. The copper fill would have a few holes (5-10, maybe), each of which would have a short (1") copper wire soldered through it and going through the back side of the board to dissipate heat. In other words, the LEDs would be one side of the board along with the fill and the wires' solder joints. The wires would all be poking out on the other side of the board. Would this provide sufficient cooling for 1W LEDs or should I look into something else? :thinking:

edit: The LEDs would be operated at the rated specs (350mA).

Thanks!
Chris

 

[frenzee]

I think what you are describing is the plated thru hole concept which works OK but not very well and it sounds much easier to do than to actually make it for the typical DIYer. Have you tried using and off-the-shelf Cree or Luxeon bare star? The dimensions are pretty close so it might work.

The OVTL01LGA is a particularly poorly designed and relatively inefficient (50 lm/W for cool white) emitter so your heat sink has to work that much harder for the same light output. The slug is also the anode so you need to isolate it from the rest of the circuit.

 

[Lighthouse one]

If the base is positive...you can get a square of aluminum--cut to 5x7, and use thermal glue -
http://www.dealextreme.com/details.dx/sku.4579
this works great...as a regular or thermal glue. Then you just have to connect one wire to the negative of each LED. You must of course be able to isolate the plate that the led's are on.
If you get an aluminum square that is 1/8 to 3/16 inch thick...it should be able to handle the heat.
I've done this with seoul Led's- and it works fine. They also have a positive base. I am taking the post of frenzee as correct that the base is positive...I personally don't know!
There may be other reason's with the project that won't allow this...but it's worth considering.

 

[chris89]

Thanks for the replies and the ideas.

I'm actually not using the white Opteks, but green and blue ones, which seem fairly efficient compared to other brands I saw. I'm controlling each color's brightness separately, so there are 4 strings of 6 LEDs. This means I can't wire all the anodes to the same copper board. What did occur to me though, based on your idea, is to have small (like .75"x.75") copper squares (I have lots of copper sheets laying around) for each LED with a small hole in the middle for the anode. The cathode will be soldered to the copper square (instead of the anode, but that's okay, right?) and the anode won't be touching anything. I'll solder a copper wire to the the anode and one to the square and then glue each square to a 5x7 PCB which will also have 24 holes, through which both wires I just soldered will be routed and soldered to the PCB. This involves a bit more work than just one big board, but I think it will work better for my application. Also, it's less work than my original idea and will probably work better. What do you think? It's a lot of work, but I want to use these LEDs. Next time I'll buy ones that include heat sinks.

Here's an image of the LED so you can get an idea of its shape, if you'd like.

Thanks again!
Chris